1. Technical Field
The present invention relates to a semiconductor chip produced in the form of a chip size package (CSP) such as an image sensor, and a manufacturing method thereof.
2. Description of the Related Art
FIG. 1 shows a cross-section of a conventional semiconductor chip comprising an image sensor and produced in the form of a chip size package. The semiconductor chip 300 comprises a sensor portion 320 on a silicon substrate 301. The front surface of the silicon substrate 301 on the light receiving surface side of the sensor portion 320 is stuck to a support 303 of glass via an adhesive sheet 304. Having part of the adhesive sheet 304 removed, an air gap 321 containing air is formed exactly on the light receiving surface of the sensor portion 320. Through holes are made in the back side of the silicon substrate 301, and a copper (Cu) rewiring line layer (rewiring layer) 311 extending through the through hole to an aluminum (Al) pad 302 is provided and electrically connected to a solder terminal 314. A silicon oxide film 308 as an insulating film for insulating from the silicon substrate 301 is formed over the copper rewiring layer 311 all over except the contact portion between the copper rewiring layer 311 and the aluminum pad 302. Further, the back side of the silicon substrate 301 is protected by a solder resist 312 except the top of the solder terminal 314.
One semiconductor chip 300 shown in FIG. 1 is obtained by originally forming a number of semiconductor sections formed in a matrix in a silicon substrate with a sheet of glass as a support and dividing it into chips by dicing. In particular, a cross-section of the adhesive sheet 304 is uncovered and exposed to the atmosphere at the side surface of a divided chip in the form of a chip size package. If the semiconductor chip 300 in this state is put in an environment of high temperature or high humidity, moisture will intrude into the air gap 321 on the sensor portion 320, causing condensation on the surface of the sensor portion 320 and the glass surface opposing thereto. This phenomenon causes the problem that a fine image cannot be obtained in the operation of the image sensor.
Several techniques are known which form a chip-size package semiconductor chip having an improved moisture-proof property, of preventing such moisture intrusion. For example, Japanese Patent Application Laid-Open Publication No. 2008-85195 (hereinafter referred to as Reference 1) discloses a technique which prevents moisture from intruding along an interface of an adhesive (spacer) for sticking a cover glass 2 and a solid-state image sensing device wafer 1 together to badly affect images of a solid-state image sensing device 3, by forming a layer of resin on the side surface as shown in the FIG. 3 of the document.